StatisticsdrillNormal approximation to the binomial
A statistics problem from Statisticsdrill. Solve it with one answer box, with a fresh sample on every attempt and the worked steps and spreadsheet function in the answer, and it is checked the moment you submit.
The task
20% of shoppers use a discount code. Among 61 independent shoppers, use the normal approximation with a continuity correction to estimate the probability that at least 17 use a code. Answers within 0.002 count, so a z table with z rounded to 2 decimals works. Round to 4 decimal places.
What this problem teaches
Check np ≥ 10 and n(1 - p) ≥ 10. Use μ = np, σ = √(np(1 - p)). At least k becomes X > k - 0.5 on the continuous scale.
A hint if you get stuck
Check np ≥ 10 and n(1 - p) ≥ 10. Use μ = np, σ = √(np(1 - p)). At least k becomes X > k - 0.5 on the continuous scale.
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